Shikimic acid and its derivatives are compounds well known in the art and can be prepared according to known methods from corresponding quinic acid derivatives by dehydration using, e.g., POCl.sub.3 in pyridine (Bestmann, H. . et al., Angew. Chemie 83, 329 [1971]; Snyder, C. D. et al., J. Am. Chem. Soc. 95, 7821 [1973]; Grewe R. et al., Chem. Ber. 98, 104 [1965]) or SO.sub.2 Cl.sub.2 in pyridine (Snyder, loc. cit.; WO 98/07685).It has now surprisingly been found that higher regioselectivity of the dehydration than described in the state of the art (up to 6:1, see Rohloff J. C., J. Org. Chem., 63:4545 (1998)) can be achieved by using ClCH.dbd.N.sup.+ (CH.sub.3).sub.2 Cl.sup.- (Vilsmeier reagent) as the dehydration reagent. The degree of regioselectivity according to the present invention is very high, e.g., in the range of 50:1 and can be as high as 100:1 for the desired stereoisomer.